Electrical Injuries Robert Primavesi, MDCM, CCFP(EM) Montreal General Hospital McGill University Health Centre Robert Primavesi, MDCM, CCFP(EM) Montreal

Electrical InjuriesElectrical Injuries

Robert Primavesi, MDCM, CCFP(EM)

Montreal General Hospital

McGill University Health Centre

Robert Primavesi, MDCM, CCFP(EM)

Montreal General Hospital

McGill University Health Centre

Electrical Injuries Goals

• To identify the important complications of electrical injuries.

• To expose the pitfalls in diagnosis.

• To explore the controversies in management.

Electrical InjuriesObjectives

Electrical InjuriesObjectives

• Define the population at risk.• Determine the factors predicting the severity of

injury.• Differentiate between high-voltage and low-

voltage injuries.• Recognize which patients require admission or

referral.• Decide which patients need cardiac monitoring.

Top 10 Myths of Electrical Injury

*

Top 10 Myths of Electrical InjuryMyth #1

Electrical Injuries Are Uncommon

Electrical InjuriesEpidemiology

Electrical InjuriesEpidemiology

• 124 deaths in Quebec 1987-1992

• 5X additional patients requiring emergency treatment

• 3-5% of all burn centre admissions

• Bimodal distribution– Toddlers

– Workforce


Voltage Is the Most Important Determinant of Injury

Electrical InjuriesFactors Determining Severity


1. V = voltage

2. i = current

3. R = resistance

OHM’S LAW: i = V / R



JOULE’S LAW:

Power (watts) = Energy (Joules) time= V x i= i2 x R

Electrical Injuries Factors Determining Severity

Electrical Injuries Factors Determining Severity

Mucous membranesVascular areas

• volar arm, inner thighWet skin

• Sweat• Bathtub

Other skinSole of footHeavily calloused palm

Skin Resistivity - Ohms/cm2

100300 - 10 000

1 200 - 1 5002 500

10 000 - 40 000100 000 - 200 000

1 000 000 - 2 000 000


High Voltage Is More Likely to Kill Than Low Voltage

Electrical InjuryFactors Determining Severity

• A momentary dose of high voltage electricity is not necessarily fatal.

• Low voltage is just as likely to kill as high voltage.

RK Wright, JH Davis. The investigation of electrical deaths: a report of 220 fatalities.J. Forensic Sci. 1980; 25:514-521.Cunningham PA. The need for cardiac monitoring after electrical injury. Medical Journal of Australia. 154(11): 765-6, June 1991.

The Extent of the Surface Burn

Determines the Severity of Injury


Electrical InjuriesPatterns of Injury


• Direct contact– Direct tissue heating

– Contact burns (entry and exit)

– Thermal burns

The Pathway the Electrical Current Takes Through the Victim Predicts the Pattern of

Injuries




Skin Resistivity

Least Nerves

Blood

Mucous membranes

Muscle

Intermediate Dry skin

Tendon

Fat

Most Bone

Electrical InjuriesEffects of 60 Hz Current

Electrical InjuriesEffects of 60 Hz Current

1 mAmp Threshold of perception5 mA Maximum harmless current6 mA Ground fault interrupter opens10 mA “Let-go” current20 mA Possible tetany of resp muscles100 mA VF threshold6 A Defibrillation20 A Household circuit breaker

opens


• Electricity Kills by Causing Myocardial Damage

• CK and/or Troponin Are Good Markers for Myocardial Damage in Electrical

Injury


• James T., Riddick L., Embry J. Cardiac abnormalities demonstrated post-mortem in four cases of accidental electrocution and their potential significance relative to non-fatal electrical injuries of the heart. American Heart Journal. 120: 143-57, 1990

• Robinson N., Chamberlain D. Electrical injury to the heart may cause long-term damage to conducting tissue: a hypothesis and review of the literature. Int J Cardiol. 53: 273-7, 1996


All Patients With Electrical Injury Require 24 Hours of Cardiac Monitoring

Electrical InjuriesCardiac MonitoringElectrical Injuries

Cardiac Monitoring

• Alexander L. Electrical injuries of the nervous system. J Nerv Ment Dis 1941; 94: 622-632

• Jensen PJ, et. al. Electrical injury causing ventricular arrhythmias. Br heart J 1987; 57: 279-283

• Norquist C., Rosen CL., Adler JN., Rabban JT., Sheridan R. The risk of delayed dysrhythmias after electrical injuries. Acad Emerg Med. 6: 393, 1999

Electrical InjuriesCardiac Monitoring

Study Voltage No. of patients

Initial ECG = Normal

Initial ECG = Abnormal

Late Arrhythmias

Purdue and Hunt

1000 48 40 8 0

Wrobel < 1000 35 31 4 0

Moran and Munster

110 – 850 42 40 2 0

Kirschmair and Denstl

220 – 900 19 15 4 0

Fatovitch and Lee

240 20 18 2 0

Cunningham 240 70 59 11 0

Kreinke and Kienst

> 220 31 29 2 0

Bailey, et. al. 120 and 240 120 119 1 0

Arrowsmith > 220 73 69 4 0

Electrical InjuriesCardiac Monitoring

• Cardiac monitoring is not justified in ASYMPTOMATIC patients,

• Or, in patients with only CUTANEOUS burns,

• Who had a normal ECG after a 120 v or 240 v injury.


ALL Patients Who Are Asymptomatic and Who Have a Normal ECG After a 120V or

240V Injury Can Be Safely Discharged From the ED



• Pregnancy– Fetal monitoring is

mandatory for pregnant patients

• Oral commisure burns• Cataracts• Delayed neuro-

psychological sequelae


The HYDRO QUEBEC GUIDELINES Provide the Standard of Care for Electrical

Injuries

Electrical InjuriesSummary - The Challenges

Electrical InjuriesSummary - The Challenges

• Electrical injuries involve multiple body systems.• Entry and exit wounds fail to reflect the true

extent of underlying tissue damage.• Electrical current may cause injuries distant from

its apparent pathway through the victim.• Controversies exist regarding indications for

admission and cardiac monitoring following low voltage injuries.

Electrical InjuriesThe Future

• Surveillance electrographique des patients ayant subi une électrisation: Étude prospective multicentrique. Investigateur principal: Benoit Bailey, MD MSc FRCPC

• 21 sites across Quebec – including RVH, MGH, MCH

• Primary objectives:1. determine the prevalence of cardiac arrhythmias in

patients on initial ECG2. determine the prevalence of late arrhythmias in patients

who undergo cardiac monitoring

• Secondary objectives:– evaluate the importance of electrical injury in Quebec’s EDs – given a normal initial ECG, evaluate if late arrhythmias

develop in patients with tetany, current across the heart, or with >1000V

– given a normal initial ECG, evaluate if late arrhythmias develop in patients with PMHx of cardiac disease, or decreased skin resistance

– evaluate the incidence of cardiac problems in the year following electrical injury

• Secondary objectives, cont’d:

– accumulate prospectively an experience with applying the Hydro Quebec protocol

– determine the utility of measuring CK, CK-MB in predicting ECG abnormalities and the development of late arrhythmias

– determine the utility of measuring Troponin in predicting ECG abnormalities and the development of late arrhythmias


“er” is an Accurate Reflection of Life in the ER

Electric Shock: What Should You Do?


The victim:

Felt the currentpass throughhis/her body

The currentpassed through

the heart

Was held by thesource of the

electric current

Lostconsciousness

Yes

No No

No1 secondor more

Yes

No

Yes

Cardiac Monitoring24 hours

Touched a voltagesource of morethan 1 000 volts

Yes

No

Yes


Page 2.


Page 2.

Touched a voltagesource of morethan 1 000 volts

Cardiac Monitoring24 hours

Has burn markson his/her

skin

The currentpassed through

the heart

Yes

NoYes

YesEvaluate and treat burns

(surgical evaluation, look for myogolbinuria, etc.)

No

Was thrown fromthe source

Evaluate trauma

No

Is pregnantEvaluate fetal

activity

No

Yes

Yes

No

BENIGN SHOCKReassure and discharge

Direction Services de SanteHydro Quebec, 1995

Documents

Electrical Injuries Robert Primavesi, MDCM, CCFP(EM) Montreal General Hospital McGill University Health Centre Robert Primavesi, MDCM, CCFP(EM) Montreal